Multipass microchannel heat exchanger

ABSTRACT

A heat exchanger is provided including a first manifold, a second manifold, and a plurality of heat exchange tubes arranged in spaced parallel relationship and fluidly coupled to the first manifold and the second manifold. At least one divider plate is arranged within the first manifold such that the first manifold has a fluidly distinct first chamber and second chamber and the heat exchanger has a multi-pass flow configuration. The first chamber is configured to receive at least a partially liquid refrigerant and has a length between about 20% and about 60% a length of the first manifold.

CROSS-REFERENCE TO RELATED APPLICATIONS

This application is a continuation of U.S. application Ser. No.14/829,151, filed Aug. 18, 2015, which claims the benefit of U.S.provisional patent application Ser. No. 62/039,161 filed Aug. 19, 2014,the entire contents of which are incorporated herein by reference.

BACKGROUND

This invention relates generally to heat exchangers and, moreparticularly, to microchannel heat exchanger for use in heat pumpapplications.

One type of refrigerant system is a heat pump. A heat pump can beutilized to heat air being delivered into an environment to beconditioned, or to cool and typically dehumidify the air delivered intothe indoor environment. In a basic heat pump, a compressor compresses arefrigerant and delivers it downstream through a refrigerant flowreversing device, typically a four-way reversing valve. The refrigerantflow reversing device initially routes the refrigerant to an outdoorheat exchanger, if the heat pump is operating in a cooling mode, or toan indoor heat exchanger, if the heat pump is operating in a heatingmode. From the outdoor heat exchanger, the refrigerant passes through anexpansion device, and then to the indoor heat exchanger, in the coolingmode of operation. In the heating mode of operation, the refrigerantpasses from the indoor heat exchanger to the expansion device and thento the outdoor heat exchanger. In either case, the refrigerant is routedthrough the refrigerant flow reversing device back into the compressor.The heat pump may utilize a single bi-directional expansion device ortwo separate expansion devices.

In recent years, much interest and design effort has been focused on theefficient operation of the heat exchangers (indoor and outdoor) in heatpumps. High effectiveness of the refrigerant system heat exchangersdirectly translates into the augmented system efficiency and reducedlife-time cost. One relatively recent advancement in heat exchangertechnology is the development and application of parallel flow,micro-channel or mini-channel heat exchangers, as the indoor and outdoorheat exchangers.

These parallel flow heat exchangers are provided with a plurality ofparallel heat transfer tubes, typically of a non-round shape, amongwhich refrigerant is distributed and flown in a parallel manner. Theheat exchanger tubes typically incorporate multiple channels and areoriented substantially perpendicular to a refrigerant flow direction inthe inlet and outlet manifolds that are in communication with the heattransfer tubes. Heat transfer enhancing fins are typically disposedbetween and rigidly attached to the heat exchanger tubes. The primaryreasons for the employment of the parallel flow heat exchangers, whichusually have aluminum furnace-brazed construction, are related to theirsuperior performance, high degree of compactness, structural rigidity,and enhanced resistance to corrosion.

The growing use of low global warming potential refrigerants introducesanother challenge related to refrigerant charge reduction. Currentlegislation limits the amount of charge of refrigerant systems, and heatexchangers in particular, containing most low global warming potentialrefrigerants (currently classified as A2L substances). Microchannel heatexchangers have a small internal volume and therefore store lessrefrigerant charge than conventional round tube plate fin heatexchangers. Although a lower refrigerant charge is generally beneficial,the smaller internal volume of microchannel heat exchangers makes themextremely sensitive to overcharge situations, which could result inrefrigerant charge imbalance, degrade refrigerant system performance,and cause nuisance shutdowns. In addition, the refrigerant chargecontained in the manifolds of the microchannel heat exchanger,particularly when the heat exchanger operates as a condenser, issignificant, such as about half of the total heat exchanger charge. As aresult, the refrigerant charge reduction potential of the heat exchangeris limited.

SUMMARY

According to one embodiment, a heat exchanger is provided including afirst manifold, a second manifold, and a plurality of heat exchangetubes arranged in spaced parallel relationship and fluidly coupled tothe first manifold and the second manifold. At least one divider plateis arranged within the first manifold such that the first manifold has afluidly distinct first chamber and second chamber and the heat exchangerhas a multipass flow configuration. The first chamber is configured toreceive at least a partially liquid refrigerant and has a length betweenabout 20% and about 60% a length of the first manifold.

According to one embodiment, a heat exchanger is provided including afirst manifold, a second manifold, and a plurality of heat exchangetubes arranged in spaced parallel relationship and fluidly coupled tothe first manifold and the second manifold. At least one divider plateis arranged within the first manifold such that the first manifold has afluidly distinct first chamber and second chamber and the heat exchangerhas a flow configuration including at least a first pass and a secondpass. A separator configured to separate a liquid and vapor refrigerantis arranged between the first pass and the second pass, and at least onebypass conduit extends from the separator and is configured to bypassone of the first pass and second pass of the heat exchanger.

BRIEF DESCRIPTION OF THE DRAWINGS

The subject matter, which is regarded as the present disclosure, isparticularly pointed out and distinctly claimed in the claims at theconclusion of the specification. The foregoing and other features, andadvantages of the invention are apparent from the following detaileddescription taken in conjunction with the accompanying drawings inwhich:

FIG. 1 is a perspective view of a known microchannel heat exchangerhaving a single pass flow configuration;

FIG. 2 is a cross-sectional view of a microchannel heat exchanger tubeof the microchannel heat exchanger of FIG. 1;

FIG. 3 a top cross-sectional view of the microchannel heat exchanger ofFIG. 1;

FIG. 4 is a cross-sectional view of a multi-pass microchannel heatexchanger according to an embodiment of the present disclosure;

FIGS. 5a-5c are various view of a multi-pass microchannel heat exchangeraccording to an embodiment of the present disclosure;

FIG. 6 are various views of a multi-pass microchannel heat exchangeraccording to an embodiment of the present disclosure;

FIG. 7 is a cross-sectional view of a multi-pass microchannel heatexchanger according to an embodiment of the present disclosure;

FIG. 8 is a cross-sectional view of a multi-pass microchannel heatexchanger according to an embodiment of the present disclosure;

FIG. 9 is a cross-sectional view of a multi-pass microchannel heatexchanger according to an embodiment of the present disclosure;

FIG. 10 is a cross-sectional view of a multi-pass microchannel heatexchanger according to an embodiment of the present disclosure;

FIG. 11 is a top, cross-sectional view of a header of a multi-passmicrochannel heat exchanger according to an embodiment of the presentdisclosure;

FIG. 12 is a cross-sectional view of a multi-pass microchannel heatexchanger having a first separator according to an embodiment of thepresent disclosure;

FIG. 13 is a cross-sectional view of another multi-pass microchannelheat exchanger having a first separator according to an embodiment ofthe present disclosure;

FIG. 14 is a cross-sectional view of another multi-pass microchannelheat exchanger having a first separator according to an embodiment ofthe present disclosure;

FIG. 15 is a cross-sectional view of another multi-pass microchannelheat exchanger having a first separator according to an embodiment ofthe present disclosure;

FIG. 16 is a cross-sectional view of a multi-pass microchannel heatexchanger having a plurality of separators according to an embodiment ofthe present disclosure; and

FIG. 17 is a cross-sectional view of a multi-pass microchannel heatexchanger having a plurality of separators according to an embodiment ofthe present disclosure.

The detailed description explains embodiments of the present disclosure,together with advantages and features, by way of example with referenceto the drawings.

DETAILED DESCRIPTION

Referring now to FIG. 1, an example of a known multi-channel heatexchanger is illustrated. The heat exchanger includes a first manifoldor header 30, a second manifold or header 40 spaced apart from the firstmanifold 30, and a plurality of heat exchange tubes 50 extending in aspaced parallel relationship between and fluidly connecting the firstmanifold 30 and the second manifold 40. In the illustrated, non-limitingembodiments, the first header 30 and the second header 40 are orientedgenerally horizontally and the heat exchange tubes 50 extend generallyvertically between the two headers 30, 40. By arranging the tubes 50vertically, water condensate collected on the tubes 50 is more easilydrained from the heat exchanger 30. In the non-limiting embodimentsillustrated in FIGS. 1-3, the headers 30, 40 comprise hollow, closed endcylinders having a circular cross-section. However, headers 30, 40having other configurations, such as a semi-elliptical, square,rectangular, hexagonal, octagonal, or other cross-sections for example,are within the scope of the present disclosure. The heat exchanger 20may be used as either a condenser or an evaporator in a vaporcompression system, such as a heat pump for example.

Referring now to FIGS. 2 and 3, each heat exchange tube 50 comprises aflattened heat exchange tube having a leading edge 52, a trailing edge54, a first surface 56, and a second surface 58. The leading edge 52 ofeach heat exchanger tube 50 is upstream of its respective trailing edge52 with respect to an airflow A through the heat exchanger 20. Theinterior flow passage of each heat exchange tube 50 may be divided byinterior walls into a plurality of discrete flow channels 60 that extendover the length of the tubes 50 from an inlet end 62 to an outlet end 64and establish fluid communication between the respective first andsecond manifolds 30, 40. The flow channels 60 may have a circularcross-section, a rectangular cross-section, a trapezoidal cross-section,a triangular cross-section, or another non-circular cross-section. Theheat exchange tubes 50 including the discrete flow channels 60 may beformed using known techniques and materials, including, but not limitedto, extruded or folded.

As known, a plurality of heat transfer fins 70 may be disposed betweenand rigidly attached, usually by a furnace braze process, to the heatexchange tubes 50, in order to enhance external heat transfer andprovide structural rigidity to the heat exchanger 20. Each folded fin 70is formed from a plurality of connected strips or a single continuousstrip of fin material tightly folded in a ribbon-like serpentine fashionthereby providing a plurality of closely spaced fins 72 that extendgenerally orthogonal to the flattened heat exchange tubes 50. Heatexchange between the fluid within the heat exchanger tubes 50 and airflow A, occurs through the outside surfaces 56, 58 of the heat exchangetubes 50 collectively forming the primary heat exchange surface, andalso through the heat exchange surface of the fins 72 of the folded fin70, which form the secondary heat exchange surface.

Referring again to FIG. 1, the illustrated heat exchanger 20 has asingle-pass flow configuration. For example, refrigerant is configuredto flow from the first header 30 to the second header through theplurality of heat exchanger tubes 50 in the direction indicated by arrowB.

With reference now to FIGS. 4-17, various embodiments of amulti-channel, heat exchanger 20 having a multi-pass configuration areillustrated. To form a multi-pass flow configuration, at least one ofthe first manifold 30 and the second manifold 40 includes two or morefluidly distinct chambers. In one embodiment, the fluidly distinctchambers are formed by separate manifolds coupled together to form thefirst or second manifold 30, 40. Alternatively, a baffle or dividerplate 80 known to a person of ordinary skill in the art may be arrangedwithin at least one of the first header 30 and the second header 40 todefine a plurality of fluidly distinct chambers therein. For example,with the addition of a divider plate 80 in the first header 30, atwo-pass flow configuration is formed. Fluid may flow from the firstchamber 32 of the first manifold 30 to the second manifold 40, in thedirection indicated by arrow B, through a first group 50 a of heatexchange tubes 50 and back to a second chamber 34 of the first manifold30, in the direction indicated by arrow C, through a second group 50 bof heat exchange tubes 50. Alternatively, the fluid may be configured toflow through the heat exchanger 20 in a reverse direction. The firstgroup 50 a of heat exchange tubes 50 and the second group 50 b of heatexchanger tubes 50 may be substantially similar, or may vary in size andshape. In addition, the number of heat exchange tubes 50 within thefirst group 50 a and the second group 50 b may be the same or different.

Regardless of the direction of flow of the refrigerant through the heatexchanger 20, the first chamber 32 of the first manifold 30 isconfigured to receive at least a partially liquid refrigerant and thesecond chamber 34 of the first manifold 30 is configured to receive avapor refrigerant. In heat exchangers 20 having a two-pass flowconfiguration, the divider plate 80 is positioned within the firstheader 30 such that the length of the first chamber 32 configured toreceive at least a partially liquid refrigerant is between about 20% andabout 60%, and more specifically between about 30% and about 50%, of thelength of the first header 30.

Another embodiment of a two-pass multi-channel heat exchanger 20 isillustrated in FIGS. 5a-5c . In the illustrated, non-limitingembodiment, the first header 30 and the second header 40 are bent toform a generally rectangular or C-shape. Arranged within the firstheader 30 is a first divider plate 80 a and a second divider plate 80 bconfigured to divide the first header 30 into a first chamber 32, asecond chamber 34, and a third chamber 36. In the illustrated,non-limiting embodiment, the first chamber 32 and the third chamber 36of the first manifold 30 are configured to receive at least a partiallyliquid refrigerant, and the second chamber 34 of the first manifold 30is configured to receive a vapor refrigerant. In one embodiment, alength of the first chamber 32 and the third chamber 36 aresubstantially identical and have the same number of heat exchanger tubes50 coupled thereto.

A first group 50 a of one or more heat exchanger tubes 50 extendsbetween and fluidly couples the first chamber 32 and the intermediatesecond header 40. A second group 50 b of at least one heat exchangertube 50 extends between and fluidly couples the second intermediateheader 40 and the second chamber 34 of the first header 30. A thirdgroup 50 c of one or more heat exchanger tubes 50 extends between andfluidly couples the third chamber 36 of the first header 30 and thesecond intermediate header 40.

During operation of the two-pass heat exchanger 20 illustrated in FIGS.5a-5c as an evaporator, two-phase refrigerant mixture is provided intothe first chamber 32 and the third chamber 36 of the first header 30(FIG. 2). The refrigerant flows through the first group of heatexchanger tubes 50 a and the third group of heat exchanger tubes 50 c,respectively, to the intermediate second header 40. From the secondheader 40, the refrigerant flows through the second group 50 b of heatexchanger tubes 50 to the second chamber 34 of the first header 30 andto an outlet formed therein. As the refrigerant flows sequentiallythrough the first and second group 50 a, 50 b of heat exchanger tubes50, or alternatively, through the third and second group 50 c, 50 b ofheat exchanger tubes 50, heat from the refrigerant is transferred to theadjacent flow of air A. As a result, a substantially vaporizedrefrigerant is provided at an outlet formed in the second chamber 34 ofthe first header 30. In another embodiment, refrigerant is configured toflow in a reverse direction through the heat exchanger 20 when operatedas a condenser.

Referring now to FIG. 3, an embodiment of a heat exchanger 20 having athree-pass flow configuration is illustrated. In the embodiment of FIG.3, the first header 30 includes a first divider plate 80 configured toform a fluidly distinct first and second chamber 32, 34 respectively.The second header 40 also includes a divider plate 80 configured todivide the second header 40 into a first chamber 42 and a second chamber44. In the illustrated, non-limiting embodiment, the first chamber 32 ofthe first header 30 is configured to receive at least a partiallyrefrigerant liquid and the second chamber 44 of the second header 40 isconfigured to receive a vapor refrigerant. The second chamber 34 of thefirst header 30 and the first chamber 42 of the second header 40 aretherefore configured as intermediate headers within the refrigerant flowpath. In embodiments of the heat exchanger 20 having a three-passconfiguration, the divider plate 80 is positioned within the firstheader 30 such that the length of the first chamber 32 is between about20% and about 60%, and more specifically between about 30% and about50%, of the length of the first header 30.

A first group 50 a of one or more heat exchanger tubes 50 extendsbetween and fluidly couples the first chamber 32 of the first header 30and the intermediate chamber 42 of the second header 40. A second group50 b of at least one heat exchanger tube 50 extends between and fluidlycouples the first chamber 42 of the second header 40 and the secondchamber 34 of the first header 30. A third group 50 c of one or moreheat exchanger tubes 50 extends between and fluidly couples the secondchamber 34 of the first header 30 and the second chamber 44 of thesecond header 40.

In embodiments where the three-pass heat exchanger of FIG. 3 isconfigured to operate as an evaporator, a two-phase mixture ofrefrigerant liquid and vapor is provided to the first or liquid chamber32 of the first header 30. From the first chamber 32 of the first header30, the refrigerant flows to the first chamber 42 of the second header40 through the first group 50 a of heat exchanger tubes 50, in thedirection indicated by arrow B. The refrigerant then flows from thefirst chamber 42 of the second header 40 to the second chamber 34 of thefirst header 30 through the second group 50 b of heat exchanger tubes50, in the direction indicated by arrow C, and from the second chamber34 of the first header 30 to the second chamber 44 of the second header40 through the third group 50 c of heat exchanger tubes 50, in adirection indicated by arrow D. As the refrigerant flows sequentiallythrough the first, second, and third groups 50 a, 50 b, 50 c of heatexchanger tubes 50, heat from air A passing there over is transferred tothe refrigerant. As a result, substantially vaporized refrigerant issupplied at an outlet formed in the second chamber 44 of the secondheader 40. As previously suggested, the direction of refrigerant flowthrough the heat exchanger 20 may be reversed, such as when the heatexchanger is configured as a condenser for example.

Referring now to FIGS. 6-10, a longitudinally elongated distributorinsert 84, as is known in the art, may be arranged within one or morechambers of the first and second header 30, 40 of the multi-passmultichannel heat exchanger 20. The distributor insert 84 is arrangedgenerally centrally within the interior volume of the header 30, 40 andis configured to evenly distribute the flow of refrigerant between theplurality of heat exchanger tubes 50 fluidly coupled thereto. In oneembodiment, particularly when the heat exchanger 20 is configured tooperate as an evaporator as shown in each of FIGS. 6-10, a distributorinsert 84 is arranged within the first chamber 32 of the first header 30configured to receive at least a partially liquid refrigerant. Thedistributor insert 84 arranged within the first chamber 32 of the firstheader 30 generally extends over the full length of the chamber 32 suchthat the liquid and vapor refrigerant mixture provided thereto will bemore evenly distributed over the length of the first chamber 32, therebyimproving the heat transfer of the heat exchanger 20. In the two-passbent heat exchanger configuration having two inlets, as illustrated inFIG. 10, a distributor insert 84 may be arranged within one or both thefirst chamber 32 and the third chamber 36 of the first header 30.

In other embodiments, as illustrated in FIGS. 6-9, a distributor insert84 may additionally or alternatively be positioned within anintermediate chamber of one or more headers 30, 40 of the heat exchanger20. As shown in FIG. 6, ae distributor insert 84 may be arranged withinand extend over the entire length of the second header 40.Alternatively, as shown in FIGS. 7-9, the distributor insert 84 mayextend over only a portion of the second intermediate header 40 toprovide refrigerant to a portion of the heat exchanger tubes 50, such asthe second group of heat exchanger tubes 50 b for example, fluidlycoupled thereto. In embodiments, such as FIG. 8, where the heatexchanger 20 has a three-pass configuration, one or both of theintermediate chambers, such as the first chamber 42 of the second header40, or the second chamber 34 of the first header 30 may include adistributor insert 70. The distributor insert 70 within each of theintermediate chambers may, but need not extend over the full length ofthe chamber.

Referring now to FIGS. 11-16, when the multi-pass multichannel heatexchanger 20 is employed in a heat pump application, one or moreseparators 90 may be fluidly coupled to the heat exchanger 20 to improvethe efficiency of heat pump. Inclusion of at least one separator 90 mayadditionally improve the flow distribution through an adjacent portionof the heat exchanger 20 and also provides an accumulator configured tomigrate refrigerant when the heat exchanger 20 operates as anevaporator, and less refrigerant is required.

As shown in FIG. 11, a separator 90 fluidly couples a first chamber 42and a second chamber 44 of the second header 40. Though the heatexchanger 20 illustrated in FIGS. 11-16 has a two-pass configuration,other configurations are within the scope of the present disclosure.When the heat exchanger 20 operates as an evaporator, the vapor andliquid refrigerant mixture provided to the first chamber 42 of thesecond header 40 via the first group 50 a of heat exchanger tubes 50flows into the separator 90. Within the separator 90, gravity causes thevaporized refrigerant and the liquid refrigerant to separate. From theseparator 90, the liquid refrigerant is supplied to the second chamber44 of the second header 40 for further heating, and the vaporrefrigerant bypasses the remainder of the heat exchanger 20 via anexternal conduit 92.

In the embodiment illustrated in FIG. 12, a valve 94 is arranged withinthe bypass external conduit 92. Although the illustrated valve 94 is acheck valve, other valves configured to limit a flow of refrigerantthrough the bypass conduit 92, such as a solenoid valve for example, arewithin the scope of the present disclosure. The check valve 94 isconfigured to allow a flow of refrigerant gas in only one directionthrough the conduit 92, such that when the heat exchanger 20 is operatedas a condenser, all of the refrigerant gas is provided directly to thesecond chamber 34 of the first header 30. When the heat exchanger 20 isoperated as a condenser, all of the refrigerant from the separator 90 isprovided to the first chamber 42 of the second header 40 and flowsthrough the first group 50 a of heat exchanger tubes 50.

In another embodiment, shown in FIG. 13, another bypass conduit 96including a check valve 98 extends from the separator and is configuredto bypass a flow of refrigerant through the first group 50 a of heatexchanger tubes 50 when the heat exchanger 20 is operated as acondenser. In such embodiments, the refrigerant provided from the secondchamber 44 of the second header 40 to the separator 90 is divided intoliquid refrigerant and vapor refrigerant. The vapor refrigerant isprovided from the separator 90 to the first chamber 42 of the secondheader 44 to flow through first group 50 a of heat exchanger tubes 50and the liquid refrigerant within the separator 90 is supplied to thebypass conduit 96.

Referring now to FIG. 14, an orifice 100 is arranged in parallel withthe check valve 94 of the external conduit 92. When the heat exchanger20 operates in a condenser mode, a small amount of refrigerant gas issupplied from the bypass conduit 92 to the separator 90 via orifice 96.The remainder of the refrigerant vapor is supplied into the secondchamber 34 of the first header 30 of the heat exchanger 20 for flowthrough a second group 50 b of heat exchange tubes 50 into the secondchamber 44 of the second header 40. The refrigerant flows through aconnecting conduit 102 into the first chamber 42 of the first header 40.The refrigerant vapor within the separator 90 is supplied to the firstchamber 42 of the second header 40 for flow through the first group 50 aof heat exchange tubes 50 to the first chamber 32 of the first header30. A check valve 104 positioned between the separator 90 and the secondchamber 44 prevents a flow of vapor refrigerant into the second chamber44 of the second header 40. If the separator 90 contains a liquidrefrigerant when the heat exchanger 20 operates as a condenser, therefrigerant charge of the system may increase. Therefore, providing asmall amount of vapor refrigerant to the separator 90 prevents theaccumulation of liquid refrigerant in the separator 90.

Referring now to FIGS. 15 and 16, a second separator 110 may be arrangedadjacent the first chamber 32 of the first header 30 and includes abypass conduit 112 fluidly coupled to separator 90. When the system ofFIG. 16 operates as an evaporator, the liquid portion of the two phaserefrigerant provided to the second separator 110 flows to the firstchamber 32 of the first header 30 and through the first group 50 a ofheat exchanger tubes 50 to the first chamber 42 of the second header 40and the separator 90. The vapor portion of the two-phase refrigerantwithin second separator 110 is provided directly to separator 90 viaconduit 112. Within the separator 90, gravity causes the vaporizedrefrigerant and the liquid refrigerant to separate. From the separator90, the liquid refrigerant is supplied to the second chamber 44 of thesecond header 40 for further heating, and the vapor refrigerant bypassesthe remainder of the heat exchanger 20 via external conduit 92.

In the embodiment illustrated in FIG. 16, bypass conduit 112 includes acheck valve 114 to limit the direction of flow of refrigerant therethrough. In addition, bypass conduit 96, including check valve 98,extends from the separator 90 and is configured to bypass the firstgroup 50 a of heat exchanger tubes 50 when the heat exchanger isoperated as a condenser. When the heat exchanger 20 operates as anevaporator, liquid refrigerant within the separator 110 will flow to thefirst chamber 32 of the first header 30 and through the heat exchanger20 as previously described. Similarly, the vapor refrigerant will flowthrough bypass conduit 112 to the separator 90 and from the separator 90into bypass conduit 92. However, when the heat exchanger is operated asa condenser, all of the refrigerant is provided to the second chamber 34of the first header 30 and flows through the second group 50 b of heatexchanger tubes 50 into the separator 90. The liquid and vaporrefrigerant is separated within the separator 90, such that the vaporrefrigerant if provided to the first chamber 42 of the second header andis configured to flow through the first group 50 a of heat exchangetubes to the first chamber 32 of the first header. The liquidrefrigerant from the separator 90 bypasses the second pass of the heatexchanger and is provided adjacent the outlet of the first chamber 32 ofthe first header 30.

By forming the microchannel heat exchanger with a multi-passconfiguration, the length of the portion of the headers 30, 40configured to receive an at least partially liquid refrigerant,specifically the first chamber 32 of the first manifold 30, andtherefore the inner volume of that portion is reduced. The refrigerantcharge of the heat exchanger 20 is also reduced as a result of thereduction in inner volume.

While the present disclosure has been particularly shown and describedwith reference to the exemplary embodiments as illustrated in thedrawing, it will be recognized by those skilled in the art that variousmodifications may be made without departing from the spirit and scope ofthe present disclosure. Therefore, it is intended that the presentdisclosure not be limited to the particular embodiment(s) disclosed as,but that the disclosure will include all embodiments falling within thescope of the appended claims. In particular, similar principals andratios may be extended to the rooftops applications and vertical packageunits.

What is claimed is:
 1. A heat exchanger comprising: a first manifold; asecond manifold separated from the first manifold; a plurality of heatexchange tubes arranged in spaced parallel relationship and fluidlycoupling the first manifold and the second manifold; and at least onedivider plate arranged within the first manifold such that the firstmanifold has a fluidly distinct first chamber and second chamber and theheat exchanger has a multi-pass flow configuration, wherein the firstchamber is configured to receive at least a partially liquid refrigerantand has a length between about 20% and about 60% a length of the firstmanifold.
 2. The heat exchanger according to claim 1, wherein the lengthof the first chamber is between about 30% and about 50% of the length ofthe first manifold.
 3. The heat exchanger according to claim 1, whereinthe heat exchanger is configured to operate as an evaporator in a heatpump system.
 4. The heat exchanger according to claim 1, wherein theheat exchanger is configured to operate as a condenser in a heat pumpsystem.
 5. The heat exchanger according to claim 1, further comprising afirst distributor insert arranged within an inner volume of the firstchamber.
 6. The heat exchanger according to claim 5, further comprisinga second distributor insert arranged within an inner volume of at leastone of the second manifold and the second chamber of the first manifold.7. The heat exchanger according to claim 1, wherein the heat exchangerhas a three-pass flow configuration.
 8. The heat exchanger according toclaim 1, wherein the heat exchanger has a two-pass flow configuration.9. The heat exchanger according to claim 8, wherein the first manifoldand the second manifold are arranged in a C-shape, the first manifoldincluding a first divider plate and a second divider plate such that thefirst manifold includes a fluidly distinct first chamber, secondchamber, and third chamber.
 10. The heat exchanger according to claim 9,wherein both the first chamber and the third chamber are configured toreceive at least a partially liquid refrigerant.
 11. The heat exchangeraccording to claim 10, further comprising a first distributor insertarranged within an inner volume of the first chamber and a second,distributor insert arranged within an inner volume of the third chamber.